Hot-air furnace



Jan. 15, 1929.

C. N. CROSS ET AL HOT AIR FURNACE Filed Aug. 13, 1927 INVENTORS (in/e; A4 Cr'ass M'l/l'am J Ingram 1 7712/ ATTORI Y5 Patented Jan. 15, 1929.

UNITED STATES PATENT OFF-ICE.

CHARLES N. CROSS, 0F STANFORD UNIVERSITY, AND WILLIAM S. INGRAM, OF SAN FRANCISCO, CALIFORNIA.

HOT-AIR, FURNACE.

Application filed August 13, 1927'. Serial No. 212,782.

This invention relates to hot air furnaces as used for the heating of homes and buildings generally and while the invention contemplates any source of heat. 1n the fire box it is particularly concerned with a gas-fired hot air furnace. The objects of the invention being to realize the reatest amount/of hcat from the fuel used, a furnace of compact form requiring little head room, and special furnace construction to attain the objects as will appear in the drawings and specification hereto. i

In the drawings Fig. 1 is a longitudmal section of one form of our furnace, Fig. 2 is an end elevation of the furnace. Fig. 3 is an enlarged sectional drawing showing the pipe connections between the fire box and the air heating drums.

Figs. 4 and 5 are respectively longitudinal section and end views of a modified form of our invention.

Briefly described our invention comprises a novel arrangement of furnace elements in horizontal extension whereby the height of the furnace is greatly reduced, and whereby the heated gases flow from the fire in one general horizontal direction toward the stack, while the cool air to be heated flows through the furnace in the opposite direction, thereby creating a counter-flow of hot gases and air and thus bringing the cool air gradually toward the more highly heated portion of the furnace and realizing the greatest extraction of heat from the heated elements of the furnace by bringing the coolest air first into cont-act'with the least heated portions of the furnace.

The invention also includes special furnace elements for more efiiciently carrying out the counter-flow of gases and transfer of heat.

In the drawings, Figs. 1 to 3 our furnace comprises a sheet metal body or casing 1 which may advantageously be covered with any suitable heat insulation (not shown) and which body takes the form of an elongated horizontally extending shell of almostany desired cross section, but preferably with rectangular flat base 2 as shown in Fig. 2 and with a semi-cylindrical top as shown, though it may be lower.

At the forward end of the horizontal shell is a cylindrical dome 4 closed on top preferably at the juncture of the curved top with the vertical sides of the body and joined by bolt flanges 6 so that the upper half can be lifted from the lower half.

Within the shell at the forward end is arranged a fire pot or box 7 preferably mounted on a foundation 8 and which box houses a burner 9 which may be for liquid or gaseous fuel as may be desired.

The burner pipe extends out of the furnace as shown and the space above the pipe is closed by an upwardly swinging door 10, while the space below is preferably fitted with an air shutter door 11 for controlling the amount of free air flowing around the burner.

The fire box is preferably arranged with an upper wall slanting generally upwardly and rearwardly to a point just above the hot gas outlet 12, and from the hot gas outlet extends a horizontal flue terminating in a stack 13 outside of the shell.

The horizontal flue comprises a series of short sections of pipe 14 in horizontally staggered relation secured to and suspending a series of air heating drums 15, 15, 15".

These drums are substantially flat and preferably elliptical boxes supported vertic-ally from the pipes as shown, the pipes entering the flat sides of the boxes close to the upper ends of the same with the inlet and outlet pipe of each box laterally offset and separated by a baflle plate 16'which connects the flat walls of the box and terminates short of bottom wall of the box so that the hot gases enteringat the top at one side of the battle must descend in one-half of the box and rise in the adjacent half for exit to the continuation of the flue on their way to the stack.

The flat drums preferably stand at various angles from the flue as shown in Fig. 2 and may even project upward as indicated at X in Fig. 1, the object being to secure as much turbulence to the gases as possible.

In practice these air heating drums 15 and the fire box 7 are preferably made of thin cast iron, and the pipe sections are cast into one of the members as at A in Fig. 3 and screwed into the adjacent member as at E in Fig. 3, thus each pipe is virtuall an integral portion of one of the cast mem ers.

Extending across thecasing or furnace shell are battle plates 17, 18, 19, 20. These plates take alternate positions between the air heating drums (thefire box 7 also being an air heating drum), plates- 18 and 20 extending from the base to about the center of the horizontal flue pipes 14 and bein notched or oerfor'ated to support them am the attache extend from the roof of the shell downward and are similarly notched for the pipes 14. Plate 17 extends from the juncture of the dome 4 and shell 1- and-is preferably curved as shown to maintain a substantially constant passage area for the ingress of fresh air to the furnace which flows along the path indicated by the small arrows, entering first at the up er open portion of the rear end of the urnace and successively down and up over the several heating drums which through their flat sides act as bafe? and fina ly up around the fire box 7 an into the dome 4 for distribution.

While the fresh air is thus entering the stack end of the furnace the hot gases'are flowing in an opposite direction through the stag ered pipes 14 and bafiied drums 15,thus' final y passing the increasingly heated fresh air over the hottest of the heated elements before distribution to the hot air pipe.

It should be noted that While we show three drums 15, 15, 15" for heatingthe incoming air, any number may be used, the cold air intake being at the tophalf of the rear end of the furnace for 1-3. or 5 drums and at the bottom half for 2-4 or 6 drums, as will readily be observed, or the fresh air inlet may be at the side or top of the furnace casing with the battles, suitably arranged to cause the counter-flow of air and hot gases.

By the construction described, any ex an-' sion of the heated parts is taken care 0 by a slight slidin of the pipes 14 along their seats in the ba cs 18 and 20 without utting any strain upon the joints, and all eating elements may be inserted or lifted out as a uniizl upon removing the upper half of the she 1.

In Figs. 4' and 5 a modification of our furnace is shown in which the shell 21 is of cylindrical form and, as shown in Fig. 3 is supported by legs 22, and the air heating drums 23 are arranged horizontally in, over lapping relation with the end of one secured by a pipe nipple directly to the other.

In Figs. 4 and 5 but two of the drums are drums, while plates 17 and 19- eases? shown, the first one overlying and resting on the fire box 24 and the'last one being supported on pipe stands 25, with the stack 26 extending vertically from the last one. Any number of drums in the relation shown may be used, and bafies 2728 extend across the shell so as to direct the incoming fresh air in direction of the arrows to produce the counter-flow of hot and cold gases as described for Fig. 1, but in this case the cold air intake is at the lower part of the rear end of the shell, and of course the cold or fresh air intake may in either construction communicate directly with the outer air or with a return duct from the rooms to be heated as done with other types of hot air furnaces.

From the showing of Figs. 1 and 4 it will be seen that the invention is susceptible of modifications while operating in substantially identical manner and any such modifications as come within the spirit of the invention are intended to be covered in the appended claims.

We claim:

1. In a hot-air furnace having a hot-air outlet, a fire-box provided with a flue extending in a lateral direction therefrom, a heating drum connected to and sus ended from said flue, and means to cause a g air to be heated about said drum and thence about said fire-box and toward said hot-air outlet.

2. In a hot-air furnace, a fire-box provided witha fiue extending tion therefrom, a plurality of heating drums connected to and spaced along said flue, and means whereby air to be heated is caused to flow about the flue and drums in a direction generally opposite to the flow of hot gases within the flue.

3. In a hot-air furnace, a fire-box provided with a flue extending in a lateral direction therefrom, a plurality of heatin drums connected to and spaced along said us, and means whereby air to be heated is caused to flow about the flue and drums and thence about said fire-box.

ow of in a lateral direc- 4.1n a hot-air furnace of the character cnaaans N. ouoss. winnraai s. meaau. 

